Open top thread cases

ABSTRACT

A sewing machine thread case acts as a container for the bobbin which holds the bottom thread on a lock-stitch sewing machine. The thread case is set within a loop taker which takes the thread from the needle and casts it around a thread case having a limited movement upon its own axis for the purpose of making a lock-stitch.

United States Patent 1191 Garry, deceased [54] OPEN TOP THREAD CASES FOREIGN PATENTS OR APPLICATIONS 1 Tlwm' Emma carry, and, 329,934 5/1930 Great Britain........................I 12/134 'Y 632,035 11/1949 Great Britain ..112/231 Manno, CalIf. 91108 by Annie W. Garry admm'stmmx Primary Examiner-James R. Hole: [22] Filed: Aug. 14, 1970 21 App]. 110.: 63,869 ABSTRACT A sewing machine thread case acts as a container for [52] US. Cl ..112/231 the bin which h lds the bottom thread on a lock- [51] Int. Cl. ..DOSb 57/14 stitch sewing machine. The thread case is set within a Fifild of Search 184 loop taker which takes the thread from the needle and casts it around a thread case having a limited move- [56] Reerenc Cited ment upon its own axis for the purpose of making a UNITED STATES PATENTS 2,583,538 1/1952 Backlin ..112/231 6 Claims, 6 Drawing Figures I\. I '-\J-\ g E H T1 1 1 ill l I ll HI H] 11 1 1 111 1 OPEN TOP THREAD CASES BACKGROUND OF THE INVENTION 1. Field ofthe Invention Of the two types of thread cases used in lock-stitch sewing machines, open top and closed top, this invention relates to the open top case well known in the art which is superior to the closed top case in that it does not have to be removed from the machine for threading. The invention relates to this type of open top thread case.

2. Description of the Prior Art Open top thread cases were designed at a time when monofilament threads were unknown. Monofilament thread is a plastic thread and highly resilient. When sewing with a machine using an open top thread case. monofilament thread coming from the top spool and to a lesser degree a top thread of multifiiament variety such as cotton. being taken by the loop taker and being carried around the case has tendencies of becoming entangled in the threading channel which carries the bobbinthread to the thread case tension. This is one of the causes for breakage of top thread of any variety and the primary cause of breakage of monofilament thread which has a great tendency to back into the channel and snarl (because of its greater ellasticity) as it is taken by the loop taker and carried arouiid the case.

OBJECTIVE OF THE INVENTION As thread coming from the top spool and coming through the needle is picked up by the loop taker and cast around the thread case it has a tendency to back lash and become entangled in the thread case bobbin thread threading channel. It is the objective of this invention to embody improvements in the open top thread case of the known art which will prevent breakage of top thread from this cause.

SUMMARY OF THE INVENTION One means of effecting an area in which top thread coming from the needle is unlikely to catch at the threading channel opening is the depressing an effective distance the top surface of the side of the threading channel which is on the same side of the channel on which bobbin thread undergoes tension as it leaves the tension spring on the outer case wall, hereafter referred to as the tension side of the threading channel. Lowering the threading point by depressing the case in a downward gradation toward the threading point makes it unlikely that top thread because of any natural elasticity will back up and catch on a surface that is lower than the level achieved by the thread in its motion on backing into that area as it is taken by the loop taker and carried around the case to form a lock-stitch.

To insure that top thread will not catch in the bobbin thread threading channel because of its said backlash motion, the side of the channel opposite the tension side is extended into a depression on the tension side of the case outer surface extending to the threading point of the threading channel, leaving a gap for bobbin thread to pass through as it passes freely through the channel to the thread case tension.

Thus covering the upper area of the threading ehannel, this extension of the case renders the catching of the top thread in the threading channel of the case impossible as it tends to whip back into that area as it is taken by the loop taker and carried around the case. This feature of the invention affords the same protection of the threading channel as the closed top case but without the inconvenience of removing the case from the machine for threading.

To facilitate the threading of the case with this new design, the case circumference is circular at all points up to the threading point at which point the tension side of the threading channel curves inward toward the bobbin, but not enough to interfere with the insertion of the bobbin into the thread case. To further facilitate threading of the case there is a depression of the inside surface of the case at channel opening on the side of the channel opposite the tension side.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top view of the entire thread case with improvements in the area of the threading channel. FIG. 2 is an enlarged view of the improved area of the top view in FIG. 1. FIG. 3 is an outside side view of the thread case as it appears with the improvements in the area of the threading channel. FIG. 4 is an enlarged side view of the improved area of the thread case shown in FIG. 3. FIG. 5 is an outside side view of the thread case as it appears with the improvement of having the tension side of the top surface of the thread case graded downward to the threading channel opening, but without the case extension. FIG. 6 is a side view of an open top thread case as it is well known in the art. The improved thread case pictured in the figures is the one used in machines such as Singer models 111, 211 and others.

DETAILED DESCRIPTION OF A SPECIFIC EMBODIMENT Referring to the drawings, 1 is the entire thread case with such features known in the art as the peripheral bearing rib 2, the cam element 3, the stop lug 7, the central tubular post 13, the bobbin holding latch 8, the bobbin inserted in the thread case 9, the tension spring 11, the threading channel 4; and the side 12 of the threading channel opposite the tension side. In the invention the tension side of the threading channel is shown depressed in a downward gradation 5 ending at threading channel opening 4 and with the circumference of the case molded inward at the threading point 10. The outside depressed area 15 makes room for the ease extension 6 which extends from the side opposite the tension side 12 across the threading channel opening 4. The inside surface of case extension 6 at threading channel opening 4 is depressed 14 for ease of threading.

What is claimed is:

I. An open top thread ease for a lock-stitch sewing machine comprised of:

a circular ease body having a fixed bottom member and a wall having an upper edge;

a central socket;

a bobbin thread threading channel cut from said wall upper edge and extending diagonally to the central area of said wall to form a threading point and a tension side of said channel;

a tension spring mounted on outer surface of said case wall opposite said threading point, said spring covering the lower portion of said threading channel; and

case to form a lock-stitch.

a bobbin thread threading channel cut from said wall upper edge and extending diagonally to the central area of said wall to form a threading point and a tension side of said channel;

a graded depression of said case upper edge in the 5 tension spring mounted on outer surface of said area immediately preceding said threading chancase wall opposite said threading point, said spring nel opening on the tension side of said channel covering the lower portion of said threading chanwhich is the same said side on which bobbin thread nel; and undergoes tension as it comes from said tension a graded depression of said case upper edge in the spring on said case wall, the lowest point of said l area immediately preceding said threading changraded depression at said channel opening being nel opening on the tension side of said channel positioned in the case circumference slightly more which is the same said side on which bobbin thread inward on said tension side of said threading chanundergoes tension as it comes from said tension nel than the other side of said channel, such said spring on said case wall, the lowest point of said graded depression thus lowering the threading l graded depression being at said bobbin thread point and being of sufficient dimensions to make threading channel opening, said lowest point of the catching of top thread in said bobbin thread said graded depression at said channel opening threading channel less likely as said top thread lowering the said tension side of said case wall comes from top spool and through the needle and upper edge to a level lower than said case wall is taken by the loop taker and carried around said upper edge on the other side of said threading channel, said lowered upper case edge being 2. A thread case according to claim 1 wherein the upper outside surface of said case immediately preceding said threading channel opening on said tension side is depressed and the upper outside surface of said case opposite said tension side of said threading channel forms an exlowered sufficiently to make the catching of top thread in said bobbin thread threading channel less likely as said top thread comes from top spool and through the needle and is taken by the loop taker and carried around said case to form a lock-stitch. 5. A thread case according to claim 4 wherein the tension which extends over said channel and said Pppefioulside of Said cause lmmeqialely P f upper Outside surface depression. forming a gap ng sald threading channel opening on said tension side between said extension and said depressed surface depressed and g large enough to allow bobbin thread to pass freely the P Qumde Sflrface of case oppos'te 531d thmugh said altered channel opening tenslon side of said threading channel forms an ex- 3 A tmead case according to claim 2 wherein tension which extends over said channel and said there is a depression of the inside surface of said exupper outside Surface depresfslon formmg a gap tension. between said extension and said depressed surface 4. An open top thread case for a lock-stitch sewing large enough to allow thread to pass freely mach-me comprised of: through said altered channel opening.

. circular Case body having a fixed bottom member 6. A thread case according to claim 5 wherein there and a wall having an upper edge. is a depression of the inside surface of said extension.

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1. An open top thread case for a lock-stitch sewing machine comprised of: a circular case body having a fixed bottom member and a wall having an upper edge; a central socket; a bobbin thread threading channel cut from said wall upper edge and extending diagonally to the central area of said wall to form a threading point and a tension side of said channel; a tension spring mounted on outer surface of said case wall opposite said threading point, said spring covering the lower portion of said threading channel; and a graded depression of said case upper edge in the area immediately preceding said threading channel opening on the tension side of said channel which is the same said side on which bobbin thread undergoes tension as it comes from said tension spring on said case wall, the lowest point of said graded depression at said channel opening being positioned in the case circumference slightly more inward on said tension side of said threading channel than the other side of said channel, such said graded depression thus lowering the threading point and being of sufficient dimensions to make the catching of top thread in said bobbin thread threading channel less likely as said top thread comes from top spool and through the needle and is taken by the loop taker and carried around said case to form a lock-stitch.
 2. A thread case according to claim 1 wherein the upper outside surface of said case immediately preceding said threading channel opening on said tension side is depressed and The upper outside surface of said case opposite said tension side of said threading channel forms an extension which extends over said channel and said upper outside surface depression, forming a gap between said extension and said depressed surface large enough to allow bobbin thread to pass freely through said altered channel opening.
 3. A thread case according to claim 2 wherein there is a depression of the inside surface of said extension.
 4. An open top thread case for a lock-stitch sewing machine comprised of: a circular case body having a fixed bottom member and a wall having an upper edge; a central socket; a bobbin thread threading channel cut from said wall upper edge and extending diagonally to the central area of said wall to form a threading point and a tension side of said channel; a tension spring mounted on outer surface of said case wall opposite said threading point, said spring covering the lower portion of said threading channel; and a graded depression of said case upper edge in the area immediately preceding said threading channel opening on the tension side of said channel which is the same said side on which bobbin thread undergoes tension as it comes from said tension spring on said case wall, the lowest point of said graded depression being at said bobbin thread threading channel opening, said lowest point of said graded depression at said channel opening lowering the said tension side of said case wall upper edge to a level lower than said case wall upper edge on the other side of said threading channel, said lowered upper case edge being lowered sufficiently to make the catching of top thread in said bobbin thread threading channel less likely as said top thread comes from top spool and through the needle and is taken by the loop taker and carried around said case to form a lock-stitch.
 5. A thread case according to claim 4 wherein the upper outside surface of said case immediately preceding said threading channel opening on said tension side is depressed and the upper outside surface of said case opposite said tension side of said threading channel forms an extension which extends over said channel and said upper outside surface depression forming a gap between said extension and said depressed surface large enough to allow bobbin thread to pass freely through said altered channel opening.
 6. A thread case according to claim 5 wherein there is a depression of the inside surface of said extension. 